1. Field of the Invention
The present invention relates to a rotation transmitter suitable for use in a compressor of an automotive air conditioning system.
2. Description of Related Art
An automotive air conditioning system, having a compressor which has a variable refrigerant discharge capacity from 0% through 100%, dispenses with an electromagnetic clutch to drive the compressor. However, in the clutch-less compressor, when the compressor shaft locks because the compressor seizes and excess load torque (shock torque) arises, the pulley driving the compressor shaft stops rotating. Thus, a V-belt driven by the engine slides against the pulley, thereby breaking the V-belt.
For solving this problem, a rotation transmitter including a torque limiting mechanism is used for interrupting the rotation transmission from the engine to the compressor when excess load torque arises due to compressor shaft lock. Here, excess load torque means that the torque difference between the pulley and the compressor shaft exceeds a threshold.
The rotation transmitter includes a pulley, an outer hub, a flange, an inner hub, and a plurality of friction plates. The pulley rotates by receiving rotation force from the engine through the V-Belt. The outer hub is connected to the pulley, and the flange is connected to the outer hub through a rubber damper. The inner hub is connected to the compressor shaft, and the plurality of friction plates are provided between the flange and the inner hub. When the compressor shaft is locked to create the excess load torque, the rotation transmission from the flange to the inner hub is interrupted. The pulley, outer hub, flange, inner hub, and friction plates are made of metal such as iron.
However, the number of parts for the torque limiting mechanism is large, thereby increasing the cost of the product. The friction plates are provided in the axial direction, thereby enlarging the axial dimension of the torque limiting mechanism. Further, most of the parts of the rotation transmitter are made of metal such as iron, thereby increasing the weight of the entire rotation transmitter.
JP-A-10-47244 discloses another conventional rotation transmitter. The rotation transmitter also includes a torque limiting mechanism interrupting rotation transmission when the compressor shaft is locked. The torque limiting mechanism includes an intermediate member having an elastically transforming portion made of thermoplastic resin. The intermediate member is connected to one of the pulley and the hub, and press-connected to the other to rotate therewith. When the compressor operates normally, the elastically transforming portion absorbs torque pulsations from the compressor shaft. When excess load torque arises (when the shaft is locked), friction heat caused by slide friction at the press-connection surface melts the elastically transforming portion, thereby interrupting the excess load torque transmission from the shaft to the pulley.
However, this conventional rotation transmitter requires a large number of parts, and a space where the intermediate member is provided in front of a bearing supporting the pulley, thereby enlarging an entire size of the rotation transmitter.